• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.9-18
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• 2013

Two-phase vapor-liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators, and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two-phase flow, it is essential to obtain detailed information about the characteristics of a two-phase flow. The characteristics of a two-phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid-dynamic force acting on the cylinder owing to the pressure distribution. A two-phase flow was pre-mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two-phase cross-flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two-phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two-phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two-phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results.

• Journal of Life Science
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• v.24 no.7
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• pp.721-727
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• 2014

Mushroom-derived ${\beta}$-glucan, a polysaccharide (GLP) isolated from the mycelium of Ganoderma lucidum, was previously shown to have inhibitory effects against tumor-bearing mice in vivo. We investigated the apoptotic effect of mushroom-derived ${\beta}$-glucan in a sarcoma-180 tumor cell- bearing mice model using an ELISA to determine the levels of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) in the mice. The morphology of the tumor cells was assessed with transmission electron microscopy (TEM). GLP was injected into the tumor-bearing mice at a dose (i.p.) of 20 mg/kg for 10 days. After 30 days, the tumor mass from the inguinal region was collected, weighed, and assayed using TEM and a TNF-${\alpha}$ ELISA kit. The tumors that developed in the mice treated with GLP were 71.4% smaller than those in the control group, showing the ability of GLP to inhibit tumor growth. The levels of TNF-${\alpha}$ in the serum of the sarcoma-180 bearing mice were 12 times greater than in the serum of the nonbearing tumor mice. An ultrastructural study demonstrated that the GLP-treated sarcoma-180 tumor cells were condensed, with rearranged chromatin. In addition, the marginated chromatin in nucleus induced the nuclear compartment, and there were many vacuolization in the cell. GLP could be an effective apoptosis-inducing compound in sarcoma-type cancers.

• The Korean Journal of Zoology
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• v.38 no.3
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• pp.405-416
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• 1995

The testis and the epididymis of sexually mature male bats were examined to investigate the process of spermiogenesis of Korean long-fingered bat (Miniopterus schreifersi fulignosus) using electron microscope. The ultrastructural findings were analysed on the basis of Lee's method (1992). Especially, we focused on the acrosome formation. The results are as follows: The spermiogenesis of the Korean long-fingered bat can be divided into ten phases on the basis of ultrastructural differentiation; three "Golgi" phases of early, mid and late stages, two "cap" and two "acrosome" phases respectively composed of early and late phases, one "maturation phase and two "spermiation" phases of early and late phases. The axoneme of sperm in the cauda epididymis is composed of nine outer dense fiber and a central singlet. The number 1, 5, 6, and 9 outer dense fibers are larger than others. In the Golgi phases, small vesicles are separated from Golgi vesicles and then appear to fuse into a large vesicle, and finally it contacd with the outerside of the nucleus. It suggests that proacrosomal material could be made in the cytoplasm before the Golgi vesicle formation and then it could be transferred into the Golgi vesicle and condensed more and more, and finally form acrosome, just as Lee;s suggestion (1992).m acrosome, just as Lee;s suggestion (1992).

• Journal of Periodontal and Implant Science
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• v.37 no.4
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• pp.859-869
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• 2007

Naked DNA and standard vectors have been previously used for gene delivery. Among these, PEI can efficiently condense DNA and has high intrinsic endosomal activities. The aim of this study is to investigate whether the cationic polycation PEI could increase the transfection efficiency of BMP expressing DNA using a vector-loaded collagen sponge model. BMP-2/pcDNA3.1 plasmid was constructed by subcloning human BMP-2 cDNA into the pcDNA3.1 plasmid vector. PEI/DNA complexes were prepared by mixing PEI and BMP-2/pcDNA3.1 and the constructed complexes were loaded into the collagen sponges. In vitro studies, BMSCs were transfected with the PEI/BMP-2/pcDNA3.1 complexes from collgen sponge. The level of secreted BMP-2 and alkaline phosphatase activities of transfected BMSCs were significantly higher in PEI/BMP-2/pcDNA3.1 group than in BMP-2/pcDNA3.1 group (p<0.05). Transfected BMSCs were cultured and mineralization was observed only in cells treated with PEI/BMP-2/pcDNA3.1 complexes. In vivo studies, PEI/BMP-2/pcDNA3.1/collagen, BMP-2/pcDNA3.1/collagen and blank collagen were grafted in skeletal muscle of nude mice. Ectopic bone formation was shown in PEI/BMP-2/pcDNA3.1/collagen grafted mouse 4 weeks postimplantation, while not in BMP-2/pcDNA3.1 grafted tissue. This study suggests that PEI-condensed DNA encoding for BMP-2 is capable of inducing bone formation in ectopic site and might increase the transfection rate of BMP-2/pcDNA3.1. As a non-viral vector, PEI offers the potential in gene therapy for bone engineering.

• Journal of Life Science
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• v.31 no.2
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• pp.149-157
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• 2021

Prunus mume Sieb. et Zucc is widely distributed in East Asia (Korea, Japan, and China), and its fruit is often used as a medication and food material. However, because most previous studies have only investigated the state of Prunus mume fruit extract, studies on the various ways of processing this extract are still needed to increase its utilization. In this study, we evaluated the physicochemical properties and physiological activities of spray-dried Prunus mume vinegar powder (SPP). The sugar content, pH, total acidity, and moisture content of the SPP were 8.90 °Brix, 3.19, 1.05%, and 3.07%, respectively. The SPP exhibited significantly high antioxidant activity in terms of DPPH radical scavenging activity (65.55%), reducing power (1.48), and hydrogen peroxide scavenging activity (48.07%). In addition, the SPP remarkably decreased the cell viability of human breast MDA-MB-231 and human skin cancer SK-MEL-28 in a dose-dependent manner. The morphological results of the treatment of MDA-MB-231 cells with SPP were distorted, shrunken cell masses. Furthermore, apoptotic bodies and nuclear condensation formed in the SPP-treated MDA-MB-231 cells. The total polyphenol and flavonoid contents of the SPP were 59.58 ㎍/g (gallic acid equivalent) and 57.56 ㎍/g (quercetin equivalent). The results of this study indicate that SPP, which has antioxidant activity and anticancer effects, can be useful in the development of natural medicines and functional food ingredients.

• Journal of Life Science
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• v.31 no.3
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• pp.321-329
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• 2021

This study examined the growth inhibitory effect of the methanol fraction of maesil (Prunus mume) extract (MMF) on LNCaP, PC-3, and RC-58T human prostate cancer cell lines. Among these cell lines, LNCaP was the most sensitive to the inhibitory effects of MMF. Observation of the morphology and apoptotic body formation in the LNCaP cells revealed morphological changes, nuclear damage, and condensation in response to MMF treatment. The suppressive effect of MMF was related to the intrinsic apoptosis pathway, as indicated by increased expression of the pro-apoptotic proteins Bax, capase-3, capase-9, and PARP and decreased expression of the anti-apoptotic protein Bcl-2. Combined treatment with MMF and the AIF inhibitor N-phenylmalemide (N-PM) indicated that MMF treatment alone had a significant growth suppression effect. The involvement of the extrinsic apoptosis pathway was also confirmed by increased expression of AIF and Endo G. The growth suppression effect of MMF was also significant when compared to the effects of a combination of the PI3K inhibitor LY294002 and MMF. The reduced expression of PI3K, p-Akt, and p-mTOR confirmed the involvement of the PI3K/Akt/ mTOR signaling pathway in regulating the anti-proliferative properties of MMF. In conclusion, the growth suppression effect of MMF in the LNCaP human prostate cancer cell line shows the possibility of using this natural product in functional foods.

• Clean Technology
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• v.29 no.3
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• pp.217-226
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• 2023

The amount of hydrogen adsorbed in arrays of single walled carbon nanotubes (SWNTs) was studied as a function of nanotube diameter and distance between the nearest-neighbor nanotubes on square arrangements using a grand canonical Monte Carlo simulation. The influence of the geometry of a triangle array with the same diameters and distances was also studied. Hydrogen-carbon and hydrogen-hydrogen interactions were modeled with Lennard-Jones potentials for short range interactions and electrostatic interactions were added for hydrogen-hydrogen pairs to consider quantum contributions at low temperatures. At 194.5 K, Type I isotherms for large-diameter SWNTs and Type IV isotherms without hysteresis between adsorption and desorption processes for wider tube separations were observed. At 200 bars, the gravimetric hydrogen storage capacity of the SWNTs was reached or exceeded the US Department of Energy (DOE) target, but the volumetric capacity was about 70% of the DOE target. At 77 K, a two-step adsorption was observed, corresponding to a monolayer formation step followed by a condensation step. Hydrogen was adsorbed first to the inner surface of the nanotubes, then to the outer surface, intratubular space and the interstitial channels between the nanotube bundles. The simulation indicated that SWNTs of various diameters and distances in a wide range of configurations exceeded the DOE gravimetric and volumetric targets at under 1 bar.

• The Korean Journal of Zoology
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• v.19 no.3
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• pp.101-112
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• 1976

1. It has been found in the karyotype of Apodemus agrarius coreae that No. 1 chromosome pair is subtelocentric and this is the new chromosome type in comparison with acro-telocentric No. 1 pair of the other subpecies. 2. It was reported in the Karyotype of Microtus fortis from USSR that the autosome consisted of 2 submetacentric, 10 metacentric and 38 acrocentric chromosomes, and that X is acrocentric and Y is small acrocentric one. In the present study, however, the autosome of M. fortis pelliceus in Korea is composed of three groups; 4 subtelocentric, 10 meta-submetacenric, and 36 acrocentric one. And X is the largest metacentric chromosome of the complement. Y is smaller acrocentric one. Thus, it has been found that the karyotype of M. fortis in Korea differs from that of the same species in USSR. In the karyotype of this red vole, two pairs of heteromorohic chromosome with respect to the size of their secondary constrictions have been shown in the acrocentric group. 3. The diploid number of Cricetulus triton nestor was found to be 28, and its chromosome size ranges from 7.5 $\\mu$ to 1.5 $\\mu$. Autosomes contains 11 large acrocentric pairs and two pairs of very small metacentric ones. This feature is simillar to that of Tscherskia triton found USSR.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.13-22
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• 2009

The composite resin, due to its esthetic quality, is considered the material of choice for restoration of anterior teeth. To get a satisfactory result in the composite resin restorations, it is necessary to choose right shade. At present, most of the commercial composite resins are based on the Vita Lumin shade guides or shade guides that are provided by their company, but color differences among them might be expected even using the same shade in various materials. This study is to measure color differences between various light-cured composite resins and shade guides and to provide the clinicians with information which may aid in improved color match of esthetic restoration. Four kinds of light-cured composite resins (Gradia Direct (GD), Z250 (Z250), Clearfil AP-X (AP-X), Esthet X (E X)) and shade guides with A2 and A3 shade were used. Three specimens of each material and one specimen of each shade guide were made. Each composite resin was filled into the Teflon mold (1.35 mm depth, 8 mm diameter), followed by compression, polymerization and polishing with wet sandpaper. Shade guides were grinded with polishing stones and rubber points to a thickness of approximately 1.35 mm. Color characteristics were performed with a spectrophotometer(color i5, GretagMacbeth, USA). A computer-controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$, $b^*$) of each specimen and shade guide. The CIELAB measurements made it possible to evaluate the amount of the color difference values (${\Delta}E^*ab$) between composite resins and shade guides. CIE standard D65 was used as the light source. The results were as follows : 1. Among the $L^*$, $a^*$, $b^*$ values of most of 4 kinds of composite resin specimens which are produced by same shade, there were significant differences(p<0.05). 2. Among all 4 kinds of composite resin specimens which are produced by same shade, there were color differences that is perceptible to human eye(${\Delta}E^*>3.3$). 3. Between most of composite resin specimens investigated and their corresponding shade guides, there were color differences that is perceptible to human eye(${\Delta}E^*>3.3$). 4. In the clinical environment, it is recommended that custom shade guides be made from resin material itself for better color matching. Shade guides supplied by manufacturers or Vita Lumin shade guide may not provide clinicians a accurate standard in matching color of composite resins, and there are perceptible color differences in most of products. Therefore, it is recommended that custom shade guides be made from resin material itself and used for better color matching.